I think 1 is not a loophole because ultimately the reason you invest is so that you can consume more down the line, and that ultimate consumption should be taxed.
I also don't see problems with 3 or 4. 3 maybe if you get a "poor" person to buy something where they'll get reimbursed and then sell it back to you, but couldn't that be fixed by limiting the amount of reimbursement they get to their total income or some fraction of it?
2 does seem like a real potential problem. Maybe businesses would also have to pay the fair tax on their purchases of capital goods, but they can offset those taxes with credits from taxes they collect further down the line? So if a farmer spends 100k on a tractor and never sells anything, then he has to pay taxes on that tractor. If he later sells 100k worth of goods, he can cancel out the taxes he had to pay on the tractor. In theory, that 100k tractor should let him collect more than 100k additional revenue overall, so this should work out.
I also don't see problems with 3 or 4. 3 maybe if you get a "poor" person to buy something where they'll get reimbursed and then sell it back to you, but couldn't that be fixed by limiting the amount of reimbursement they get to their total income or some fraction of it?
2 does seem like a real potential problem. Maybe businesses would also have to pay the fair tax on their purchases of capital goods, but they can offset those taxes with credits from taxes they collect further down the line? So if a farmer spends 100k on a tractor and never sells anything, then he has to pay taxes on that tractor. If he later sells 100k worth of goods, he can cancel out the taxes he had to pay on the tractor. In theory, that 100k tractor should let him collect more than 100k additional revenue overall, so this should work out.